1. Field of the Invention
The invention refers to a sliding chair, a sliding plate and a ribbed plate, respectively, for railway switches or railway crossings, comprising friction-reducing sliding members made of synthetic plastic material the friction-reducing sliding members being releasably mounted within recesses in the sliding chair and the plates, respectively.
2. Description of the Prior Art
In railway switches comprising a deflecting device, the tongue rails rest on sliding chairs and are shiftably supported thereon. In switch constructions that have the frog itself swivelably mounted, different constructions are known in which part of the frog is slidingly supported on a plate member or the whole frog swivelably rests on sliding plates. Swivelable constructional parts are also known in connection with railway crossings, noting that, in all known constructions, a suitable lubrication for sliding support must be provided and, respectively, ease of swivelability on the sliding plates, the sliding chair and the ribbed plates, respectively, in a reliable manner. When lubricating the sliding supports in a usual manner, there results high maintainance costs, because the sliding supports must be supplied with lubricant at regular time intervals. Lubricating oils additionally suffer from the drawback of having varying lubricating properties under the influence of the weather conditions, and the lubricating oils completely lose their lubricating properties in cases of increased contamination. For this reason, it has already been proposed to utilize in place of lubricants sliding members of synthetic plastic material and reduced friction. From DE-OS 27 05 122 there has, for example, become known a railway switch for railway vehicles comprising a deflecting device wherein the tongue rails rest on sliding chairs, noting that friction-reducing sliding members of synthetic plastic material are provided between the parts sliding upon each other. In this known construction, the sliding members of synthetic plastics material were provided on the bottom side of the tongue rails at least within the area of the sliding chairs. Furthermore, it is known to use sliding plates of railway switches coatings consisting of an organic material, noting that such synthetic plastic material shall have a sufficient flexibility, a sufficient impact strength and a sufficient abrasion resistance even at low temperatures. Also, such sliding members of synthetic plastic material are subjected to reduced+wear but still require maintainance work at regular time intervals. For the purpose of facilitating the maintainance work, it has already been proposed in the EP-A 232 726 to mount within a frame, which is removably locked within a recess of the sliding chair, a plurality of sliding elements consisting of self-lubricating material. The self-lubricating material proposed for this construction was graphite-bronze being press-seated within the frame. A construction utilizing graphite-bronze was selected because obviously no type of sliding inserts were found which have sufficient stability and can rapidly and simply be replaced without the use of expensive tools or equipment.